The present invention is directed to an apparatus for electrolytical surface treatment of bulk goods, particularly for the electro deposition of aluminum from an aprotic, oxygen-free and water-free, aluminum-organic electrolyte. The apparatus comprises a tank for the acceptance of the treatment bath, an arrangement for contacting the goods with one pole of an electrical source, at least one electrode arranged in the treatment bath and having the opposite polarity of the one pole and at least one vibratory conveyor comprising a helically ascending conveyor track for transporting of the goods through the treatment bath.
Aluminum deposited from an aprotic, oxygen-free and water-free, aluminum-organic electrolyte is distinguished by its ductility, low number of pores, corrosion resistance and ability to be anodized. Since the access of air will effect a considerable diminution of the conductivity and the useful life of these electrolytes due to the reaction of the electrolytes with atmospheric oxygen and atmospheric humidity, the electro-plating must be undertaken in a treatment apparatus which operates under air exclusion or a protective atmosphere. In order for the access of air to be prevented during loading and unloading, these treatment facilities operating under an air exclusion utilize admission and discharge locks. These admission and discharge locks are fashioned as gas locks, as liquid locks, or as a combined gas-liquid lock and are equipped with conveyor means for conducting the goods to be treated through the locks.
U. S. Pat. No. 4,427,518, which is based on the same German application as European Pat. No. 0,070,011, discloses an apparatus or facility for the electro deposition of metal, wherein bulk goods to be electro-plated are introduced into an electro-plating drum rotatably arranged in an electro-plating tank. The introduction of the goods is by an admissions station provided with conveying means. The goods are then conducted through the electro-plating drum, which is provided with a screw conveyor on an inside wall and then discharged at an exit station which is provided with a conveyor means. The electro-plating drum, which is provided with perforations, is, thereby, connected as a cathode, whereas the anode is arranged in the inside of the electro-plating drum. For the electro-deposition of aluminum from oxygen-free and water-free, aluminum-organic electrolyte, the electro-plating drum is constructed to be closed ga tight and the space lying above the electrolyte level is charged with an inert gas. In addition, the admission and exit stations for the apparatus are additionally equipped with liquid locks.
In mass electro-plating, the bulk goods to be electro-plated must be held together during the galvanic processing so that every individual part is electrically contacted. On the other hand, the goods to be electro-plated should be spread out as far as possible so that the metal deposition can occur on as large as possible surface of the goods and an optimum uniform current density is guaranteed on all parts. Another essential precondition for achieving faultless metal coatings having a uniform layer thickness is an adequate mixing of the goods to be electro-plated during the galvanic processing. In what we refer to as a suspension-electro-plating device, this is achieved by transmitting an oscillating rotational motion onto the goods vessel filled with the goods to be electro-plated and the vessel is immersed into the electrolyte (see the announcement in Galvanotechnik Vol. 75, 1984, No. 11, page 1399). The electrolyte exchange is also improved at the same time by means of an oscillatory motion of the vessel containing the goods. Given an apparatus or facility comprising an electro-plating drum, rotation of the drum suffices for the moving and mixing of the goods to be electro-plated. The individual parts are conveyed upward to a greater or lesser distance toward the top dependent on the form and wall friction of the drum and then roll or slide back down. An apparatus for mass electro-plating should also be equipped with conveyor means for transporting the goods to be electro-plated through the electrolyte with either a continuous or interval-wise admission and removel of the goods for electro-plating being enabled by the conveyor means in combination with corresponding admission and exit stations. Finally, both the motion of the goods, and the mixing as well as the transporting of the goods through the bath of the electrolyte should be undertaken so that a gentle treatment of the goods is guaranteed and sensitive parts are likewise not mechanically damaged during the galvanic processing.
An apparatus or system which is disclosed in U.S. Pat. No. 3,649,490 is used for electrolytic surface treatment of bulk goods and largely meets the demands mentioned hereinabove. A vibratory conveyor having a helically ascending conveying track is provided for the transport of the goods to be electro-plated through the electrolyte. However, the helical conveying track secured to a central carrying column and suspended into the treatment bath from above can only be realized with a limited length for structural reasons and for reasons of stability. For this reason, the dwell time of the bulk goods in the treatment bath is too short in many applications for electrolytic surface treatment.
U.S. Pat. No. 4,253,916 discloses an electro-plating apparatus or system for bulk goods, wherein an annularly designed tank is placed in vibration and the goods on the helical floor of the tank are thereby constantly kept in motion. Given this electro-plating facility, the dwell time of the goods in the treatment bath can be adapted to the respective requirements. However, since the tank together with the treatment bath contained therein and the bulk goods must be placed in vibration, only a slight structural height with a correspondingly low throughput or output can be realized.
In Swiss Pat. No. 594 072, another type of electro-plating apparatus for bulk goods is disclosed. In this apparatus, the galvanic metal deposition is undertaken on a helical ramp arranged in the treatment bath. This helical ramp is placed in vibration with the assistance of a vibrator. The upper turns of the ramp serves as a helical conveyor which transports the goods up for better mixing, so that they can in turn fall back onto the ramp. Since the space of the helical ramp is tightly restricted, only a low output or throughput can be obtained. Moreover, the removal of the completely galvanized parts from the ramp involves considerable cost.
The problems, which were recited above, with regard to mass electro-plating also occur in the same way, or at least in analogous ways, in other processes for electrolytic treating of bulk goods. Examples of other processes of electrolytic treating of bulk goods include electrolytic pickling in acid or caustic solutions, electrolytic degreasing in alkaline baths and electrolytic polishing. Dependent on the type of electrolytic surface treatment, the bulk goods are either connected to a cathode or an anode, for example, in electrolytic polishing, the goods are connected to an anode.